北部湾盆地福山凹陷晚始新世物源示踪与源汇系统耦合

北部湾盆地福山凹陷古近纪“盆小源多”、沉积体系复杂多变，源汇配置关系及源汇耦合模式研究有待深化。通过地震前积反射、锆石U-Pb定年、重矿物组分和砂岩百分含量多方法开展福山凹陷流沙港组一段上亚段沉积物源示踪，厘定源汇配置关系，进而建立福山凹陷晚始新世不同源汇耦合模式，以指导有利储层预测。结果表明，南部斜坡带、西部陡坡带和东部陡坡带可见明显前积反射；永安、花场地区锆石均表现为与海南隆起物源类似的双峰年龄特征；福山凹陷重矿物组合可以分为4类，即：西部朝阳地区，东部金凤地区，南部西侧美台、永安地区，南部东侧花场、白莲地区；南部美台、花场、白莲沿线可见砂岩百分含量高值，向北可延伸至永安地区，西部朝阳地区、东部金凤地区可见砂岩百分含量中值。综合分析认为，福山凹陷晚始新世发育南部海南隆起、西部临高凸起和东部云龙凸起3大物源，其中海南隆起物源又可分为东、西两支。进一步将晚始新世福山凹陷划分为海南隆起—南部斜坡带、临高凸起—朝阳陡坡带和云龙凸起—金凤陡坡带3个次级源汇系统。从源汇控储的角度来看，南部海南隆起—南部斜坡带源汇系统中的水下分流河道为优质储层发育有利区带。

Sediment provenance and source-to-sink coupling of the Late Eocene Fushan Sag in Beibu Bay Basin

The Paleogene Fushan Sag in Beibu Bay Basin is characterized by small area, multiple sources as well as complex and variable depositional systems, and the source-to-sink correlation and coupling are poorly understood. Methods: By multiple methods of seismic foreset reflection, zircon U-Pb dating, heavy mineral assemblage and distribution of sandstone percentage, the provenance of upper submember of the first member in Liushagang Formation was investigated to determine the source-to-sink relationship, and then different source-to-sink coupling models of the Late Eocene Fushan Sag were established to guide favorable reservoir prediction. Results:The results show that the seismic profiles from southern gentle slope, western steep slope and eastern steep slope zones exhibit obvious foreset reflection; similar to those from Hainan Island, the zircon U-Pb age spectra of Yongan and Huachang areas are characterized by double peak ages; the heavy mineral assemblages of Fushan Sag can be classified into four categories, i.e., Chaoyang area in the western steep slope zone, Jinfeng area in the eastern steep slope zone, Meitai and Yongan areas in the west side of the southern gentle slope zone, and Huachang and Bailian areas in the east side; the high percentage values of sandstone can be seen along Meitai, Huachang and Bailian areas in the southern gentle slope zone, which can be extended to Yongan area in the north, and the median percentage values of sandstone can be seen in Chaoyang area in the west and Jinfeng area in the east. Conclusions:Comprehensive analyses indicate that the Late Eocene Fushan Sag had three major sources, i.e., Hainan Island in the south, Lingao Uplift in the west and Yunlong Uplift in the east, of which the source of Hainan Island can be divided into east and west branches. The Late Eocene Fushan Sag is further divided into three secondary source-to-sink systems, including Hainan Island-southern gentle slope zone, Lingao Uplift- western steep slope zone and Yunlong Uplift-eastern steep slope zone. From the perspective of source-to-sink system, the underwater distributary channel in the source and sink system of Hainan Island-southern gentle slope zone is a favorable zone for high-quality reservoir development.